The present disclosure is related generally to the field of microelectronic devices, and more specifically but not exclusively, to adapting openings in a reference layer to contribute towards achieving a differential impedance in a circuit.
Impedance matching may be a useful design technique for reducing noise or distortion in high-speed applications. During differential signaling on a high-speed bus, for example, an impedance mismatch between package traces and motherboard traces can be a source of distortion and signal loss. Matching impedances may be difficult, however, due to varying effects of different materials in the semiconductor device. In some cases, minimizing trace width and varying trace spacing or geometry within a package substrate layer may be used to achieve a particular matching impedance. Manufacturing capabilities and the high density of semiconductor devices, however, can often limit the effectiveness of such approaches.